The sensitivity of SARS-CoV-2 antigen tests in the view of large-scale testing

  1. Pavel Drevinek
  2. Jakub Hurych
  3. Zdenek Kepka
  4. Ales Briksi
  5. Michal Kulich
  6. Miroslav Zajac
  7. Petr Hubacek

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Abstract

Objectives

Antigen tests have recently emerged as an interesting alternative to SARS-CoV-2 diagnostic PCR, thought to be valuable especially for the screening of bigger communities. To check appropriateness of the antigen based testing, we determined sensitivity of two point-of-care antigen tests when applied to a cohort of COVID-19 symptomatic, COVID-19 asymptomatic and healthy persons.

Methods

We examined nasopharyngeal swabs with antigen test 1 (Panbio Covid-19 Ag Rapid Test, Abbott) and antigen test 2 (Standard F Covid-19 Ag FIA, SD Biosensor). An additional nasopharyngeal and oropharyngeal swab of the same individual was checked with PCR (Allplex SARS-nCoV-2, Seegene). Within a 4-day period in October 2020, we collected specimens from 591 subjects. Of them, 290 had COVID-19 associated symptoms.

Results

While PCR positivity was detected in 223 cases, antigen test 1 and antigen test 2 were found positive in 148 (sensitivity 0.664, 95% CI 0.599 - 0.722) and 141 (sensitivity 0.623, 95% CI 0.558 - 0.684) patients, respectively. When only symptomatic patients were analysed, sensitivity increased to 0.738 (95% CI 0.667 - 0.799) for the antigen test 1 and to 0.685 (95% CI 0.611 - 0.750) for the antigen test 2. The substantial drop in sensitivity to 12.9% (95% CI 0.067 - 0.234) was observed for samples with the PCR threshold cycle above > 30.

Conclusions

Low sensitivity of antigen tests leads to the considerable risk of false negativity. It is advisable to implement repeated testing with high enough frequency if the antigen test is used as a frontline screening tool.

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  1. ScreenIT

    SciScore for 10.1101/2020.11.23.20237198: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementIRB: The study was approved by the hospital Ethics Committee (ref no EK-1286/20).
    Consent: Antigen tests and PCR: Upon the subject’s consent, we sampled three separate nasopharyngeal swabs and one additional swab from the oropharynx.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variableThe mean age of the cohort was 40 years (age range 12 to 78 years), 44.7% were males.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    In reference to the aim of our study, i.e. to check the effectiveness of the mass testing with antigen tests, another limitation of the study is the bias in selection of the subjects who were in most cases indicated for the examination due to symptoms or contact tracing. One can expect that the population-wide screening would include higher rate of asymptomatic people with low viral loads as well as healthy persons which in turn would lead in even higher false negativity and false positivity rates (18). To conclude, in our opinion, the risk and rate of false negativity of antigen tests may have a significant negative impact on the effectiveness of outbreaks containment as it is crucial to early identify any positive person, including the ones with initially low viral load. Not to miss them, a single round of testing, which is likely the case when a population-wide screening is ordered, seems insufficient and inadequate. Instead, the strategy based on repeated testing with high enough frequency (2) needs to be implemented if the antigen test is used as a frontline screening tool.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2020.11.23.20237198v1 on medRxiv